Editor's note: Julian E. Zelizer is a professor of history and public affairs at Princeton University's Woodrow Wilson School. He is completing a book on the history of national security politics since World War II, to be published by Basic Books. Zelizer writes widely on current events.

Julian Zelizer says support for bigger government is riding on the success or failure of the stimulus bill.

PRINCETON, New Jersey (CNN) -- Last week, Obama told an audience in Florida that if his economic recovery plan does not work, "then you'll have a new president."

Regardless of whether Obama meant that he would not run again or that he would be defeated, he referred to how much is at stake with the federal programs that were debated over the past two weeks.

But Obama severely understated what is really at stake. Far more than his presidency is at risk. The $787 billion economic recovery legislation, combined with financial bailout likely to cost more than a trillion dollars, has opened up a huge debate in American politics over the role of the federal government in an economic crisis.

For several decades, starting in the 1930s with the New Deal, liberals argued the federal government should be the first responder in times of economic crisis. They made a series of arguments to support their claim.

Only the federal government could marshal the kinds of funds that were necessary to strengthen the nation's economic infrastructure (ranging from bringing electricity to rural America to building our highway program).

Only the federal government could limit the severity of the financial risk that Americans confronted when our economy went bad. And, most importantly, only the federal government could spend the amount of money that was needed to sustain economic growth when Americans had empty pocketbooks.

Starting with Ronald Reagan's historic supply-side tax cut in 1981 and lasting through President George W. Bush's second tax cut in 2003, conservatives countered those liberal arguments.

While conservatives accepted the need for big government in practice (despite their rhetoric) when it came to economic recovery, Republicans argued that tax cuts and deregulation were the answer.

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The right said that the best thing that government could do to is to lower the tax burden of business as well as upper middle class and wealthy Americans so that they would invest their money and take risks that were needed to grow the economy.

Conservatives said that government spending did not strengthen the infrastructure of the economy but only produced "boondoggle" projects.

Every program, they said, was another "Big Dig," referring to the overpriced and disastrous tunnel-building project in Massachusetts.

Conservative economists argued that the "stagflation" in the 1970s -- the combination of stagnation and inflation -- undermined the promise of liberal economists following the advice of economist John Maynard Keynes, who advocated government spending to energize the economy.

"Government is not the solution to our problem," Reagan said, "government is the problem."

Now Obama and the Democratic Congress have dramatically changed the conversation. The economic freefall that the United States faces has discredited Republican ideas about tax cuts and deregulation. But now the burden is on Democrats to provide a compelling alternative. iReport.com: Share your thoughts on the stimulus plan

Stepping into power during a moment of grave crisis and uncertainty, Congress approved an economic recovery bill and the White House will start work on a huge financial bailout program that would have been impossible to even conceive of after the 2004 presidential election, when the conservative activist Richard Viguerie said, "Now comes the revolution."

Even a few months ago, commentators were talking about the reality of a "center-right" America that would severely limit President Obama's options. Yet what we are seeing constitutes a kind of government intervention in the economy that America has not experienced for decades.

If these programs succeed, Democrats will have revitalized a core argument of modern American liberalism: that the federal government, primarily through spending and regulation, has to be the first responder when we face an economic crisis.

The stimulus package and financial bailout will become the symbol to show why government intervention does not work in times of economic crisis. This, according to liberal economists, is the danger posed by the compromises that were made by the administration -- both in asking for less than most economists think is necessary and then settling for an even lower figure in the negotiations.

The effects of new policies on politics can be enormous. When Americans enjoyed economic growth in the 1950s and 1960s, liberals were able to point to the New Deal and subsequent federal programs as powerful evidence that government intervention can benefit the nation.

When Americans enjoyed renewed economic growth during the middle of the 1980s and much of the 1990s, conservatives looked back toward Reagan's 1981 tax cut as proof that lowering the tax burden had boosted the economy.

Regardless of Obama's future, it is likely that Americans will be talking about this economic recovery and financial bailout programs years from now as they reach conclusions about whether the government can lift this country out of an economic crisis.

The opinions expressed in this commentary are solely those of Julian Zelizer.